These small copepods ate up algae, preventing it from sinking to great enough depths for long-term sequestration to work. Photo: AWI

Researchers investigating ocean iron fertilization in the Southern Ocean as part of the Lohafex project have reported back that their results show that the geo-engineering technique could not have a major impact on absorbing excess carbon dioxide from the atmosphere, at least not in that region of the world's oceans:The BBC quoted Victor Smetacek of the Alfred Wegener Institute as saying,

There's been hope that one could remove some of the excess carbon dioxide—put it back where it came from, in a sense, because the petroleum we're burning was originally made by the algae. But our results show this is going to be a small amount, almost negligible.

What it means is the Southern Ocean cannot sequester the amount of carbon dioxide that one had hoped.

The algal bloom in fact attracted large numbers of zooplankton predators, such as these amphipods, which ate the copepods, which ate the algae.... photo: AWI

In the experiment, researchers fertilized a 300 square kilometer patch of the ocean, which saw a burst of algal growth. For long-term sequestration to work, enough of that algae would have to sink to the bottom of the ocean. However, within two weeks the algae were being eaten by copepods, which then were eaten by amphipods. The result being that far less carbon dioxide made its way to the sea floor than had been anticipated.